Impact of light irradiation on black tea quality during withering

Abstract

Black tea manufacture usually involves the processes of withering, cutting, fermentation and drying. The aim of present study was to evaluate the effect of the relationship between the quality and withering with different light sources (ultraviolet, yellow, blue, purple, orange, red, cyan, green and white) an quality attribute of tea. The results indicated that the yellow, orange and red light withering significantly improved the aroma and taste, imparting the tea a sweet flavor and a fresh and mellow taste. Tea treated with yellow light was scored highest the sensory scores and showed the highest content in catechins, theaflavins, amino acids and aroma components, followed by the orange and red light treatments. The black tea withered with ultraviolet light showed a strong astringency, probably resulting from low contents of theaflavins, amino acids and soluble sugar. The green light irradiation remarkably damaged the aroma and taste of the tea, leading to a strong greenish flavor and an astringent taste, probably owing to the lowest contents of chemical compositions. No significant cumulative effect was found in the hybrid light withering treatments. Therefore, monochromatic yellow, orange and red lights were suggested for withering the black tea to improve its overall quality.

Keywords

Black tea Withering Light Sensory quality Chemical components

Abbreviations

C

Catechin

EC

Epicatechin

ECG

Epicatechingallate

EDTA

Ethylene diaminetetraacetic acid

EGC

Epigallocatechin

EGCG

Epigallocatechingallate

EI

Electron impact

GC

Gallocatechin

GC–MS

Gas chromatography-mass spectrometer

He

Helium

HPLC

High performance liquid chromatography

NADPH

Reduced nicotinamide adenine dinucleotide phosphate

SDE

Simultaneous distillation and extraction

TF1

Theaflavin

TF2A

Theaflavin-3-gallate

TF2B

Theaflavin-3′-gallate

TF3

Theaflavin-3, 3′-digallate

Zeyi Ai and Beibei Zhang have contributed equally to this work and should be considered co-first authors.

Notes

Acknowledgements

This study was supported by Key Projects in the National Science & Technology Pillar Program during the 25-year Plan Period (2012BAF07B05-2) and the Fundamental Research Funds for the Central Universities (2662015PY136).